Ti:CffinCAL INFOaiLiTIOK Oti BUILDING ilATERIALS

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x^'OR USE lA TEE DBSIGL OF LOv/-COSE HOUSING

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T-U: NATIOLixL 3UHSAU OF'STEUDARDS

UHITBj STAHLS DSPARBEHT OF GOM'.ERGB

i'/ASHIxIGTOi'j j C»

OctoEer' 7 , 19*57

ABES_IVF^

The iollov.'infi: report on adh.es ives for bonding floor coverings to su.h~

floors represents a preliminary study of the subject, based on a revieu

of literature and information furnished by manufacturers and others, con- cerning the laying and maintenance of floors. In some instances the information availabla v/eurants definite recoeinienda-tions. In other cases,

however, it is not possiblo to say which adhesive is the most suitable or

to tell how it should be applied to secure the best results. There are many questions which can be answered only on the basis of thoroughgoing

experimental studies and systematic observations on floors in service.

Pending the time when such investigations can be made, the present re- port is offered for such assistance as it may afford the xi,rchitect, the

builder, s.nd the owner in connection with flooring problems.

^ • Preparation o

f__ 3 ub-f1 o ors

1. Condi tion of Sub-floors

s

'The condition of the sub- floor is the most important single factor

in satisfactory installation of floor covering. The sub-floor should be

hard, firm, level, smooth, clean, and dry, in order that it will not detract from the w.earing qualities of floor covering or cause cracks and

irregularities therein. The dryness of the sub-floor is essential for

successful bonding of wood, linoleum, cork tile and rubber tile. Therefore, such floor coverings should not be laid until appropriate tests

show that sub-floor is sufficiently dry.

Hew concrete sub-floors should be trov^eled to a true, even surface,

at a level belov; the finished grade equal to the thic;aiess of floor cov- ering to be applied.

V/ooden sub-floors should not be installed on or below gr-.de without adeq'uate provision for waterproofing. The surface of a new wooden

sub-floor should be brought up to a level below the finished floor grade

of l/l6 inch plus thiclcness of floor covering.

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2 . 'Tes'^^ for Darnpne s s

;

The presence of moistore in concrete may he determined as follow’sTorn a ring of patty about 6 inches in diameter and l/Z inch high at each

point on the floor to he tested. Sprinicle sn small amount of anlij'-drous copper sulphate or calcium chloride within these rings, covering each ring v;ith a piece of dry window glass, pressing the glass dovm on the putty to seal

enclosed chemical from outside air. Leave in place from 12 to 24 hours.

Anliydrous copper sulphate, which is white when dry, will turn blue if moisture is present. Calcium chloride will he dissolved by moisture, leaving a stain.

The moisture content in wood may he determined in a few seconds by the

electrical resistance method. ’’The instruments for this purioose have two

pairs of sharp metallic terminals that can he quickly embedded in the wood,

batteries for supplying an electric current tlirough the wood intervening het’vveen the two terminals, and a means for reading the resistance in the electric circuit directly in terms of the moisture content of the wood holding

the terminals.”!

3. Us e of F elt over Wooden Sub-floors;

In the installation of resilient floor covering on a wooden sub-floor,

use of felt lining is generally considered necessar.y (eaccept for wooden floor

coverings) to take up irregular movements caused by expansion and contraction

of the v/ood.

The felt ordinarily employed for this pirrpose is l/l6 inch thick and may

be either dry or asphalt-saturated, according to kind of floor covering and

contemplated use. A lignin paste is frequently used to bond felt to subfloor.

II. Kinds of Adhesives

1. Prop erties

;

An adh.esive is a combination of a binder, a filler, and a carrier. The

binder supplies the adliesive properties 5 the filler contributes to the me- chanical strength, reduces the shrinkage in cooling or drying, and improves

the resistance to shock; and the carrier imparts a consistency to the adhesive

which makes it easy to apply, after which it evaporates.

Forest Products Laboratory ”v/ood Handbook” (193b) may be obta,ined

from the Superintendent of Documents, \/ashington, D. C. (price 25 cents)
An ideal a^dhosive should have the follov/ing chai'actoristics

;

(1) It should 'be easily and quic-kly applica'ble at ordin...ry temperatures,

v/ithour having to apply prolonged pressure.'

(2) It should permit a normal ”set-up” after ap]plication to su'b-floor

v'ithin a. short period, and it should ho.ve high adhesive strength to properly

adiiore to su'b-floor and to the particular type of floor covering for which

it is intended,

(3) It should retain its adhesive properties utider various conditions,

particularly where there is moistui’e caused 'by flooding of floor in cleaning,

and at tne same tirae be impervious to moisture.

(4) It should be suificiontly elastic to hold floor coverings in place,

SOI f icientl;/- plastic to v.ithsto.nd shocks without fracture, and should retain

these qualities for anj" length of time at any temperature to vhich the floor

may be subjected.

(5) It should be sufficiently plo.stic at ordinary temperatures so that

the bond will not break when t'me floor covering and sub-floor expa,nd or con- tract differentially in varying atmosrjheric conditions.

(6) It should have good self-healing properties so that, in case the

bond is broken, it will reseal readily.

(7) It should not have a. perma.nent odor, no vola.tile solvents to be

locked in, and should contain no substances to discolor or injurethe floor

coverings.

(e) Its cost should be reasonable,

^ * -^^thesives for Flopr Cove rings

:

-.uheslves in general use are;

(a) Portla,nd Cement Mortar

A stiff, rather dry mortar of portland cement a/nd saeid in the proportions

of one part cement to one a.nd one-half or tvo pa.rts sand is widely used.

(b) Asphalt Cement

Either native or petroleuiii aspha.lt, or a mixture of the tv^o, mav be used

as a base for asphalt cement. A mineral filler, such as clay, or a fibrous

material, suc'n as as'bestos, is often added to bind the base a::d for..; a toogher mass when set.

Asphalt cement may be applied to the sub-floor in any one of three forms;

hot; "cut-back'’ ’with light petroleum hydrocarbons, such as mineral spirits;

or emulsified with water.

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Hot; The Hot application is limited in scope and it appears to He test | adapted to the small 'oxi.it type of floor covering or to repair work. There is ' probatly less danger of *'hleoding” with r. hot application than there is with i a cold. See AB-5-25 and -iP-5-25, Federal Specification SS-A-706, ’’Asphalt

|

(For Use in) Road and Pavement Constraction”.^

Cat-hack: The solvent for the cat-hack form of application mast have a | comparatively narrow distillcation range, and must not contain heavy ends which - j might leave the asphalt cement soft whan floor covering is laid or caaso pro- '-j grossive deterioration of the covering. |

?! One advantage claimed for cat-hack comerit is that ixi hoing compoondod at ’^1 the scarce, a proraixtaro of this type is more likely to prodaco good rosalts ; in the hands of ordinary floor layers, since no complicated instractions or ! procaations are necessary. This argarsent, hov^ovor, is eq.aa].ly applicable to j the emalsion tj'pe.

j

Finals i on; An asphalt emalsion mast set, i.e., the water vehicle mast

evaporate, before floor coverings can he laid over it. The time for this

| action may he controlled largely by the amorxit of water ased to emalsify the j' asphalt. Under favorable conditions, an emulsion v/ill become tacky in from j 20 to 40 minates, and will retain this tackiness indefinitely . One advantage ij of the emulsified cement is that there is plenty of time to get it well leveled ) off before it sets.

Several objections have been raised against the emulsion type. One is I that it shrinks upon drying, the amount of shrinlzago depending upon the quan- | tity of \.ator in the emulsion when it is applied. But, it should bo remom- bored that the sirrinkage largely takes place before floor covering is laid. i Another objection is that it will re-ernalsify if water reaches it before it

| is thoroughly sot, although, lundor favorable conditions it vi/ill set in a short time. Still another objection is the diffic'ulty of determining just

when the water has evaporated sufficiently to produce the best results. This source of trouble, however, according to floor experts, is over-emphasized.

An e:q)erienced floor layer is able to determine the proper time for laying

floor covering by the vi/ay the adhesive sticks to the finger when pressed

' lightly on the surfo-ce. 1

FrLmers ; Asphalt primers, which contain more water or solvents than | corresponding asphalt cements, are often -used to increase penetration of

asphalt into the concrete sub-floor, hiereby strengthening mechanical anchorage. Either type of primer must be allowed to thoroughly set before : cement is applied. For cut-back primer see Federal Specification SS-A-701,

"Asphalt-Primer; (for) Roofing and i/atorproof ing".l i

Ivlay be obtained from Superintendent of Documents, Washington, D. G.

(Price 5 cents)

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(c) Lignin Paste

Lignpii obtained from waste sulphite liquor in the manufact'ure of paper,

is widely used as a base for linoleujn paste with clay added as a filler.

Svaporation of the water leaves a tenacious mass v/hich sets in a relatively

short time, has good adhesion, and is flexible and durable. It is soluble

in water, however, and should not be used where water is likely to be present.

Lignin paste does not become hard and brittle in service, a serious objection to dextrin paste which it has replaced.

(d) he sin Cement

Solutions of shellac, resins, and g'ums, in alcohol, acetone, etc., to

'which a filler is added, such as clay or short-fiber asbestos, form a group

of "resin cements" for use with some of the more resilient floor coverings.

These cements are sometimes claimed to be waterproof, but are really so only

to a limited extent.

/They are more elastic than lignin paste, and do not appear to crystallize

under conditions of light traffic,

(e) Hubber Cement

Hubber cement is a solution of rubber in gasoline, benzene, carbon tetrachloride or other organic solvent. Because of the high viscosity, rubber con- centrations in excess of 12 percent are not generally employed. In making

cements the raw rubber is first masticated or "broken down" by milling. This

process has a marked effect on the properties of the resulting solution. The

best cement is produced when the rubber is given a smaill amount of hot milling.

(f) Latex Cement

Latex cements are made from natural rubber latex w/hich is a suspension

of rubber particles in an aqueous medium. They have a much lo’..'er viscosity

than rubber cements and yield stronger and better aging films on drying,

Centrifugally concentrated latex, containing about 60 percent of solids, is

used extensively in making late:, cements, "However, these concentrates a-re rel -tively unstable and quick-drying, so tlmt protective argents must be used

when compounding".

"The adhesive properties of latex caji he modified within

wide limits by compounding with emulsions of certain materials capable of producing tackiness, such as casein, resins,

etc. Casein is a protective colloid and when put into solution with a weak alkali (0,5 percent LHg) it is very effective as a stabilizer for latex. The use of casein results

in an absorbed film or coating around each latex particle

very similar to the n^/Gural protein sheath. Thus, it in- creases the effective size of th'i particles, and hence, in

general, increases the viscosity of the system. It also

"See "Latex in Industry", by H. J. "o'ble

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makes the particles more resistant to coagulative influences. Casein has the property of increasing the stiffness'

of a latex film, hut it also decreases its resistance to

water. A softening agent, such as stearic a,cid, mineral

oil, or paraffin wax is o|^ten added to reduce the excessive toughness of latex."

Fillers, such as clay or zinc oxide, are added for the purpose of modifying properties of the rather film obtained, and in order to give the latex

compo'und suitahle working characteristics, as for sprea.ding.

IV. PI oor C 0 ver ing

s

1 . Materials

;

Materials for floor coverings may he divided according to resilience

and 'warmth into five groups:

(1) lion-resilient floors of concrete, ceramic mosaic tile, stone mosaic

terrazzo, etc., which are good conductors 'of heat.

(2) More resilient floors, such as asphalt tile, hut which are nearly

as good conductors of heat as concrete.

(3) S'emi'-elastic floors, such as wood, which are comparatively non- heat-Gonduct ing, hut not as resilient as linoleum or ruhher.

(4) Hesilient floors, such as linoleum or ruhher, v/hich are not as good

non-conduc bors of heat as wood.

(5) Hesilient floors, such as cork, which are the hast non-conductors

of heat and the most resilient of all floor coverings.

2'. Sele ction of Floor Cove r

i

ngs ;

The choice of materials to he used for floor coverings is determined h;/ kind of suh-floor, hy the location of the floor area in the building, and by

the t;>^e of occupancy of the room. The adhesive to he used is determined

largely by the type of floor covering to which it is to he applied. (See

Table 1, page 7)

1 See "Latex in Industry", hy R. J. ITohle.

S
•Tr^LZ I - ITI.OOR COVER II'IGS AND ADHESIVES

Floor Covering ; Sab-floor : Adhesive

-IP }

Material Form • Material Location

Asphalt Tile

or plank

• Concrete

' or vi/ood

Anyl Asphalt

emalsion

Ceramic

(mosaic

)

Tile • Concrete

• Settings bed

Any Portland ce- ment mortar

Cork Carpet

or tile

‘ Concrete

or wood

Above

grade

Ligiiin*

paste

Linoleum Strip

or tile

• Concrete

• or wood

Above

gradel

Lignin

paste or resin cement

Rahher Strip

or tile

• Concrete

’ or v/ood

Above

gradel

Lignin

paste or resin rabber

or latex ce- ment

V/ood Strip

or block

• Concrete

or wood

A.sphalt

cement' for

hot application or cathack

Hlith layer of felt over v;ood sah-floor.

2On rfie;.ihrane—waterproofed concrete sab—floor, on or belov/ grade.
V . Use of Adhesives

1. Choice of Adhesives: '

-ti-dhesives , as indicated in fc-hlo 1, should he selected according to the , type of floor covering with which they are to he used. I

(1) For ceramic raosaic tllei portland cement.

(2) For asphalt tile and wood; asphalt cement.

(5) For linoleum and cork; lignin paste or resin cement. -i

(4) For ruhoer; lignin paste, resin cement, rwhher cement, or latex i cement .

'

I 2 . Method of App l icati o_n : |

(a) Ceramic Mosaic Tile^

!

j Ceramic mosaic tile is bonded monolithically to a special concrete base j' 2 1/2 inches to 4 inches thick hy means of a mortar setting-hed from 1/2 to i 1 1/4 inches thick of rather dry mix. This hed is smoothed off and leveled ^ with a straight edge, and dry portlswid cement is ’’dusted” over the surface. J The mortar reaches its initial set in a few minutes, and the tile may then he

| laid and ’’hoaten in”. i

(h) Asphalt Tile

Asphalt tile is laid in asphalt emulsion. Concrete suh-floors should

first hv treated with a primer which should he allowed to drj* before cement

is applied. Asphalt emulsion should he applied math a straight-edged trowel

.and spread very thinly (about 0.01 inch) to prevent the adhesive from oozing i up between the tiles and causing discoloration.

One brand of emulsion cement has an average spreading capacity of 150

square feet per gallon. Tils may be laid on this cement after a drying period;

of half an hour. ;

Asphalt tiles are bonded directly to concrete sub-floors; but on v/ooden

sub-floors they should be installed over saturated felt or its equivalent,

m/hile the felt may be attached to the wood with lignin paste.

(c) Vi/bod

Uooden floor coverings are bonded directly to either concrete or wooden

sub-floors with hot or cu’o-back asphalt cerrient. The thickness of cement

should be kept less than l/s inch to prevent ’’bleeding”, altho'ugh agreement

on thickness is lacking.

^Associated Tile Ms-n-ufacturers ’ delated Study,

8
Drying periods for cements will necessarily De greater for laying v;ood

floors than for asphalt tile, hecause of the greater thiclciesses of ceraent era- ployed,

(d) Linoleur.i, Cork Composition Tile, Cork Tile, and Cork Carpet

Lignin paste is used almost exclusively to hond each of the four hasic

tjipes of cork floor coverings to concrete or woodon suh-floors. It is usually

applied with a notched spreader to insuxo uniforra thickness, and has an average spreading capacity of 120 square feet per gallon.

The use of dry lining felt is recoiaraondod over v;oodon suh-floors, to

which it is ceraented with lignin paste.

where there is likely to he excessive spillage of water, asphalt-sat'orated

felt is substituted for dry felt, and resin cement is used to hond floor cov- ering to felt. Hesin cement is usually spread with a straight-edged trowel,

and it has an average spreading capacity of 70 square feet per gallon.

Finished cork-hase floors raust he thoroughly rolled and should he weighted

down for several hours to insure complete adhesion.

(e) Suhher

Tools required and method employed for installing ruhhor floor coverings

are identical with those used for first-class linole'um installations. Lignin

paste is used for applying saturated felt to wood s’uh-floors.

Various adhesives such as, lignin paste, resin ceraent, ruhher ceraent, and

latex cement, are used to hond ruhher floor coverings to the felt or directly

to concrete suh-floors. The adhesives should he spread soraewhat thinner than

for laying linoleura, hecause ruhher does not ahsorh the adhesive. Detailed

information reganding the application of ruhher and resin cements is given in

"Adhesion Frohloras in Connection with Ruhher Flooring", Inbernational Ruhher

association, The Hague (19S0).

VI. Types of Failures Due^ to Lack of Bond

Frequent failures of floor coverings to give satisfactory adhesion to

suh-floors are, almost wifnout exception, the result of the ujusuitahle condition of S’uh-floor or, to a far less extent, to the imsuitahle condition of

floor covering when laid, or to improper maintenance afterwards, although

faulty workmanship and poor quality of materials contribute to such failures.

There is at present no successful method of dealing v.-ith a sub-floor tr.at is not dry at time of laying floor covering, ileither is there an adlaesive

which will withstand flooding or improper maintenance of finisr.ed floor.

1 . Expansi on and Cent ra c t ion;

Expansion and contraction of a floor covering in plane of floor, resulting from normal changes of temperature or himiidity, do not cause failiu'-e of

a good hond, if proper expansion joints are provided.

9
2,

Buckling and 1 ing

;

L,hc1c of exnansion joints, or 'onequal expansion of sections of noor cover-1

inp lacause of its unsuitable condition when laid, may produce aisplacemen, o "It^Sf noor covering out of its plane in form of buck ing c^^

part!

canle .0 elastic

Sat trSlll hold floor coverlne rigidly to suh-floor and still retarn certain

other desirable properties of the ideal adliesive.

3, Loosening of Pieces

Single tiles or unit wooden hloohs occasionally become loose, especially

during the early life of the floor, because of

j „ traffic. Such oiecos when taken up ana carefully inlaid, ael^om

Sve1SL:r;rohle. lithe case of rubber flooring, moisture is an important

factor oontributlr,g to the loss of bond. This and otner factors are aealt I wi?; in the book, hdheslon Problems in Connection with 2ubber Flooring , International- Rubber Association, Bhe Hague, (1930).

4. llaintena^^

mere should be proper coordination in the choice of adhesives wi+Ji the

materials used to finish and maintain the floor covering.

Lrt‘to use stains or waxes dissolved in liquids which are ° f

"

-hesives in order to nrevent solvent action if seepage shoula occui tuirough

JoiSrin floor covering. Moreover, the use of too much water in cleaning

floor should be avoided. (See Bureau of Standards Letter Circul r ^ u. ,

'’The Care of Floors")^

This displacement invaria.blj'’ destroys bond wibh

1

‘May be obtained free upon request from the Na

.iifeshington, D. C.

ational Bureau of Standards,

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